Suspension ceiling grid systems typically provide grid members interconnected to provide rectangular or square openings in which panels are positioned and supported. Some of such systems provide generally U-shaped grid members or runners which provide channel-like recesses between panels. An example of such system is described in U.S. Pat. No. 3,835,614. Such recesses cooperate with the panels in such ceiling systems to provide a delineation between panels which interrupts the ceiling surface in a pattern which provides an aesthetically pleasing appearance. However, such runners are relatively wide and provide a wide recess which tends to dominate the appearance of the ceiling. Further, such runners require substantially more material than the typical tee runner grid system.
In most prior art grid systems, the grid members or runners are formed with a cross section of an inverted "T" and provide a lower or exposed flat surface formed by the oppositely extending flanges on which the panels are supported. In such systems, the assembled grid and panels of the ceiling appear as a planar system in which the panels appear to provide a surface interrupted by a pattern of flat, relatively wide bands. Although such systems are widely used, some people find the bands undesirable. Examples of such systems are illustrated in U.S. Pat. Nos. 3,501,185; 3,693,303; and 4,108,563.
Further, in such systems it is necessary to size the panels with sufficient clearance so that they may be easily inserted and removed, and in some instances where the panels are not accurately sized and the panel is not accurately centered, the panel can shift to one side of the grid opening and leave an unsightly crack or opening between a panel edge and the adjacent grid flange.
It is also known in some instances to provide a generally T-shaped grid member with a downwardly open slot shaped to receive T-fasteners which can be positioned in the slot and used to support various equipment or fixtures. Such grid systems are often used in hospitals where patient privacy curtains or other equipment can be mounted on the T-fasteners. An example of such systems is illustrated in U.S. Pat. No. 4,021,986.